1. Field of the Invention
The present invention relates to means for removing spotwelds generally and, more particularly to a novel rotary tool for removing spotwelds on metal parts as are found, for example, in automobile bodies and the like.
2. Background Art
Especially in the field of automobile body repair, it is often necessary to remove damaged sheet metal panels or or remove such panels for access to other parts of the automobile. Typically, these sheet metal panels are attached to other sheet metal panels or metal structural members by means of spotwelding.
There are three types of conventional tools available to assist in removing spotwelded sheet metal panels. One type is a drill with a clamping fixture having one leg which fits about the spotweld to apply pressure from the opposite side of the area of the spotweld to force the drill into the spotweld. Apart from being relatively expensive, this tool requires that access be had to the rear of the spotwelded area, requiring either that use of the tool be limited to those areas where such access is present or that a portion of the panel be cut away to permit the access. The latter requires additional labor and may preclude re-use of the panel if re-use is desired. Also, use of the tool is limited by the depth of the clamping fixture. A second type of tool is essentially a circle cutter which cuts a circle in the sheet metal panel to be removed, thus freeing the panel but leaving a plug of the panel with the spotweld thereon attached to whatever the panel had been welded. A disadvantage of this type of tool is that additional labor is required to grind away the plug before a new panel can be installed. A third type of tool for removing spotwelds is a cutter having two cutting edges at the face thereof and having a pilot drill disposed along the center axis and extending outwardly from the face thereof to center and guide the cutter into the spotweld, thus cutting away the spotweld and a small portion of the sheet metal panel. While this type of tool is relatively inexpensive, it has been found that it dulls easily, dulling being noticeable after removing only about 25 spotwelds, which requires that greater force be used to remove spotwelds. A total of about 150 spotwelds may be removed before the tool must be resharpened or replaced. Additionally, the tool must be used at relatively low rotational speeds, less than 600 rpm, since it is prone to breakage if it snags on the edge of the sheet metal. One manufacturer of the latter type of tool recommends not tightening the chuck of the drill very tight so that the cutting tool can spin in the chuck if it snags. That, of course, greatly limits the amount of force that can be applied, thus increasing cutting time.
Accordingly, it is a principal object of the present invention to provide a tool for removing spotwelds which can be used to remove a large number of spotwelds before being sharpened or replaced.
It is a further object of the invention to provide such a tool that is easily and economically constructed.
It is an additional object of the invention to provide such a tool that can be used at relatively high speeds.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.